Dc-dc conversion device

Abstract

A DC-DC conversion device includes four semiconductor switch elements 101 to 104 in a full-bride configuration on the primary side of a transformer 2 . With this configuration, it is possible to increase the turn ratio of a primary winding 21 and secondary winding 22 of the transformer 2 and thus increase a voltage V 21 generated in the primary winding 21 , and to decrease a current flowing through the primary winding 21 of the transformer 2 and thus decrease breaking currents of the semiconductor switch elements 101 to 104 . Consequently, it is possible, by using an input voltage detection circuit 9 and an oscillator circuit 8 , to prevent a decrease in power conversion efficiency particularly when an input DC voltage from a power source 1 is high and the switching frequencies of the semiconductor switch elements 101 to 104 are high.

1 . A DC-DC conversion device for use with a DC power source having a positive terminal and a negative terminal, comprising:
 input stage means, connected to the DC power source, for generating AC power; and   output stage means for rectifying and smoothing the AC power generated by the input stage means,   wherein the input stage means includes:
 a first series arm, formed by connecting first and second semiconductor switch elements in series, the first semiconductor switch element being connected to the positive terminal of the DC power source, and the second semiconductor switch element being connected to the negative terminal of the DC power source, the first and second semiconductor switch elements being connected to one another at a first node; 
 a second series arm, formed by connecting third and fourth semiconductor switch elements in series, the third semiconductor switch element being connected to the positive terminal of the DC power source, and the fourth semiconductor switch element being connected to the negative terminal of the DC power source, the third and fourth semiconductor switch elements being connected to one another at a second node; 
 first to fourth capacitors connected in parallel to the first to fourth semiconductor switch elements; 
 first to fourth diodes connected in parallel to the first to fourth semiconductor switch elements; 
 a resonating reactor; 
 a resonating capacitor, the resonating capacitor, the primary winding of the transformer, and the resonating reactor being connected in series between a common node between the first and second nodes; 
 an input voltage detection circuit which detects an input DC voltage received by the input stage means from the DC power source; and 
 pulse generating means which alternately and cyclically generates a first pulse which turns on the first and fourth semiconductor switch elements and a second pulse which turns on the second and third semiconductor switch elements, and which causes the frequencies of the first and second pulses to rise when the input direct current voltage is high and drop when the input direct current voltage is low, based on a result of the input direct current voltage detection in the input voltage detection circuit, so that a constant direct current voltage is output from the DC-DC conversion device without depending on the input direct current voltage. 
   
     
     
         2 . The DC-DC conversion device according to  claim 1 ,
 wherein the pulse generating means includes an oscillator circuit that has a variable oscillating frequency and that generates synchronizing signals by oscillating, the first and second pulses being generated in response to the synchronizing signals generated by the oscillator circuit, and   wherein the pulse generating means causes the oscillating frequency of the oscillator circuit to rise when the input direct current voltage is high and drop when the input direct current voltage is low based on the result of the input DC detection by the input voltage detection circuit.   
     
     
         3 . The DC-DC conversion device according to  claim 2 , further comprising:
 an output voltage detection circuit which detects a DC voltage output by the output stage means,   wherein the pulse generating means, which generates the first and second pulses in response to the synchronizing signals output by the oscillator circuit, includes a pulse-width modulation control circuit which controls the respective pulse widths of the first and second pulses based on result of the DC voltage detection in the output voltage detection circuit so that the direct current voltage output by the output stage means maintains a target value.   
     
     
         4 . The DC-DC conversion device according to  claim 1 , wherein the first to fourth capacitors are parasitic capacitances interposed in the first to fourth semiconductor switch elements. 
     
     
         5 . The DC-DC conversion device according to  claim 1 , wherein the first to fourth diodes are parasitic diodes interposed in the first to fourth semiconductor switch elements. 
     
     
         6 . The DC-DC conversion device according to  claim 1 , wherein the resonating reactor is provided by leakage inductance of the transformer. 
     
     
         7 . The DC-DC conversion device according to  claim 2 , wherein the resonating reactor is provided by leakage inductance of the transformer. 
     
     
         8 . The DC-DC conversion device according to  claim 3 , wherein the resonating reactor is provided by leakage inductance of the transformer. 
     
     
         9 . A DC-DC conversion device for use with a DC power source having a positive terminal and a negative terminal, comprising:
 input stage means, connected to the DC power source, for generating AC power; and   output stage means for rectifying and smoothing the AC power generated by the input stage means,   wherein the input stage means includes:
 a first series arm, formed by connecting first and second semiconductor switch elements in series, the first semiconductor switch element being connected to the positive terminal of the DC power source, and the second semiconductor switch element being connected to the negative terminal of the DC power source, the first and second semiconductor switch elements being connected to one another at a first node; 
 a second series arm, formed by connecting third and fourth semiconductor switch elements in series, the third semiconductor switch element being connected to the positive terminal of the DC power source, and the fourth semiconductor switch element being connected to the negative terminal of the DC power source, the third and fourth semiconductor switch elements being connected to one another at a second node; 
 a series circuit connected between the first and second nodes, the series circuit including the primary winding of the transformer; 
 an input voltage detection circuit which detects an input DC voltage received by the input stage means from the DC power source; and 
 pulse generating means which alternately and cyclically generates a first pulse which turns on the first and fourth semiconductor switch elements and a second pulse which turns on the second and third semiconductor switch elements, and which causes the frequencies of the first and second pulses to rise when the input direct current voltage is high and drop when the input direct current voltage is low, based on a result of the input direct current voltage detection in the input voltage detection circuit, so that a constant direct current voltage is output from the DC-DC conversion device without depending on the input direct current voltage.